With all due respect, you are incorrect. Mono, when played in stereo devices is not a single channel; it is two identical channels.
Download a left-channel only mp3 file and open it in any player. Tested here: Creative Wave Studio, WavePad, Windows Media Player, PowerDirector, MPC-HC and Videopad. Every one of those devices plays the file as left-channel only, which is the correct behavior. It will not be heard center channel, no matter where pan is set. If panned right, there will be no sound, because there is nothing on the right channel.
Incorrect behavior in some earlier VP versions would cause a a left-channel only file to play on both channels - unless a stereo track was added to the project. Then the left-channel track would be heard only on the left channel (as it should be), necessitating the workaround described in a related thread.
UPDATE: The incorrect behavior is still evident in 6.23 for a non-center-channel mono file. See below.
That procedure converted the left-only file into a true mono file - equal volume on both channels - resulting in a perceived centered audio image.
This is so-called center-channel MONO. All voice recordings that are to be played on a stereo device should be recorded in this manner.